Quarterly Compounding
Problem: Discuss steps for calculating compound interest for quarterly compounding.
1. State the problem and define variables.
Define the principal $P$, the annual nominal interest rate $r$ expressed as a decimal, the number of compounding periods per year $n$, and the time in years $t$.
For quarterly compounding set $n=4$.
2. Write the compound interest formula.
The accumulated amount after $t$ years is given by the formula
$$A = P\left(1 + \frac{r}{n}\right)^{nt}$$
For quarterly compounding substitute $n=4$ to get
$$A = P\left(1 + \frac{r}{4}\right)^{4t}$$
3. Calculation procedure.
Given values for $P$, $r$, and $t$ compute step by step: first compute $r/4$, then compute $4t$, then compute the base $1+r/4$, raise it to the power $4t$, and finally multiply by $P$.
4. Worked numerical example.
Let $P=1000$, $r=0.05$, and $t=3$.
Compute $r/4=0.0125$.
Compute $4t=12$.
Compute base $1+0.0125=1.0125$.
Compute $1.0125^{12}\approx1.16075$.
Multiply by $P$ to obtain $A\approx1000\times1.16075=1160.75$.
5. Interpretation and tips.
The investment grows to about 1160.75 after 3 years with quarterly compounding at 5 percent.
For greater accuracy use a calculator or software to evaluate the power directly.
If the rate is given as a percentage convert it to decimal by dividing by 100 before substituting into the formula.
Final answer: The general formula for quarterly compounding is
$$A = P\left(1 + \frac{r}{4}\right)^{4t}$$
and the worked example gives $A\approx1160.75$.